I used to volunteer there, and when I did the popcorn was warm, fluffy and made regularly. There were a variety of fixings, including nutritional yeast (essential), though not any sort of cheese powder (an oversight).
Though that was a few years ago, so things may have changed since then.
The consensus I've heard is that the Hollywood has the best popcorn in Portland. They make it fresh (it's not pre-popped and bagged like a lot of other places). They don't have real butter, but the butter topping they use is good (soy-based, I think). Certainly some of the best popcorn that I've had in Portland, if not the best.
Hollywood uses a special hybrid kind of popcorn that produces fluffier popcorn with less hulls. I can't remember the name of it, but they explained it that way when I was a volunteer there. It is terrific popcorn.
The butter topping is the typical soybean oil stuff that most theaters use. It may or may not have dairy solids in it; if it's important to you, just ask them.
IT'S BEEN AWHILE SINCE I'VE EATEN THE POPCORN AT THE HOLLWYOOD (SIX MONTHS, MAYBE? IT WAS AT THE JOHN WOO DOUBLE FEATURE); BUT WITHOUT HESITATION, I'D SAY THAT THE ROSEWAY HAS BETTER POPCORN. AND BETTER SEATS.
@ VEGAN, SHUTTING UP NOW!!: I've heard people at the theater ask that question, and I'm pretty sure the answer was 'yes'. But not being vegan myself I didn't really absorb the answer. Someone there will know, ask them, but I think it is.
Though that was a few years ago, so things may have changed since then.
The butter topping is the typical soybean oil stuff that most theaters use. It may or may not have dairy solids in it; if it's important to you, just ask them.